Rangelia

Rangelia is a genus of parasitic alveolates of the phylum Apicomplexa.

History
This organism was first described in Brazil in 1910. This discovery was not confirmed until 2011 when experimental transmission of the organism showed its pathological capabilities.

Description
This parasite's normal life cycle involves wild canids and ticks. Domestic dogs are accidental hosts. It has been reported from Argentina, Brazil and Uruguay.

This parasite is transmitted by ticks.

After injection into the vertebrate host the parasite migrates to endothelial cells of the capillaries. The parasites lie within parasitophorous vacuoles that have a trilaminar membrane with villar protrusions. An apical complex is present which includes a polar ring and rhoptries but lacks a conoid.

The parasites may also invade erythrocytes and leukocytes.

Clinical features
The disease caused by infection with this parasite is known as rangeliosis. In Brazil it is also known as nambi-uvú (bleeding ears), peste de sangue (bleeding plague) and febre amarela dos cães (yellow fever of dogs).

Presentation
The clinical manifestations of this disease are anaemia, jaundice, fever, hepatomegaly, splenomegaly, lymphadenopathy, haematochezia and persistent bleeding from the nose, oral cavity and the tips, margins and outer surface of the pinnae. Other features include lethargy, loss of appetite, weakness, weight loss, dyspnoea, petechiae and haematemesis.

Laboratory findings
These include regenerative anaemia, spherocytosis, icteric plasma, leukopenia due to neutropenia, thrombocytopenia, eosinopenia and bilirubinuria. The alanine aminotransferase, aspartate aminotransferase and creatine kinase levels may be raised. The gamma-glutamyltransferase, urea and creatinine levels remain normal.

Histology
Langhans type multinucleate giant cells may be present in the lymph nodes and the choroid plexus.

Erythroid hyperplasia may be present in the bone marrow.

Diagnosis
Diagnosis may be made by demonstrating the organism in the bone marrow or by serology.

Differential diagnosis
This includes babesiosis, ehrlichiosis, leishmaniasis and leptospirosis.

Treatment
Treatment with diminazene aceturate has been shown to be effective.

Vectors
Amblyomma aureolatum

Hosts

 * Crab-eating fox (Cerdocyon thous)
 * Pampas fox (Lycalopex gymnocercus)